Underwater towed vehicle



June 16, 1964 E. c. BRAINARD ll, EIAL 3,137,264

UNDERWATER TOWED VEHICLE Filed Nov. 15, 1961 2 Sheets-Sheet 1 FIG. I

INVENTORS EDWARD C. BRAINARD lI COURTLAND B. CONVERSE JAM ATTOR N EYS 2 Sheets-Sheet 2 FIG. 5

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FIG. 6

INVENTORS BRAINARD II ATTORNEYS Jun 1 1964 E. c. BRAXNARD n, EIAL UNDERWATER TOWED VEHICLE Filed Nov. 15, 1961 FIG. 8

EDWARD C.

COURTLAND United States Patent 3,137,264 UNDERWATER TOWED VEHICLE Edward C. Brainard H and Courtland B. Converse, Marion, Mass., assignors to Braincon Corporation, Marion, Mass., a corporation of Massachusetts Filed Nov. 15, 1961, Ser. No. 152,396 3 Claims. (Cl. 114-235) This invention relates to a novel and improved underwater towed vehicle particularly adapted to carry instrumentation for oceanographic research.

T heincrease in oceanographic research has resulted in a distinct need for improved methods which will increase the speed at which oceanographic surveys and the like can be completed. In such surveys, it is a common practice to tow a submerged instrumented vehicle behind a research ship. The towed vehicle may, for example, carry a hydrophone and amplifier, the signals from which are transmitted to recording instruments on the towing vessel. One of the primary difliculties encountered in such an arrangement is that conventional underwater vehicles of the type concerned cannot be towed satisfactorily at speeds in excess of four to five knots. This places an undesirably low limitation on the speed in which a given survey can be completed inasmuch as it limits the speed of the towing vessel over a given course.

Accordingly, it is the primary object of this invention to provide a novel and improved underwater towed vehicle which will permit oceanographic surveys to be conducted at vessel speeds which are materially greater than are now possible.

It is a further object of this invention to provide such a novel and improved vehicle which depends on hydrodynamic forces to depress the vehicle rather than mere weight, which will have a materially improved lift over drag ratio, which will have a low acoustic noise characteristic, and in one aspect will be acoustically transparent, which will have improved stability about the yaw, roll and pitch axes, and which will be lightweight, cornpact and of simple, yet rugged, construction.

Other objects will be in part obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the drawings:

FIG. 1 is a top plan view of an underwater towed vehicle constructed in accordance with this invention;

FIG. 2 is the air foil cross section of the wing of the vehicle of FIG. 1 as taken along the line 22 of FIG. 1;

FIG. 3 is a side elevational view of the embodiment of FIG. 1;

FIG. 4 is a front elevational view of the embodiment of FIG. 1;

, FIG. 5 is a side elevational view of a faired cable for towing the vehicle of this invention;

FIG. 6 is a cross sectional view along the line 6-6 of FIG. 5;

FIG. 7 is a side elevational view, partly in section, of an alternative embodiment of this invention; and

FIG. 8 is a cross sectional view taken substantially along the line 8-8 of FIG. 7.

With reference to the drawings, and particularly FIGS. 1 to 4, an underwater towed vehicle constructed in accordance with the present invention comprises a body, generally indicated at 10. The body 10 is essentially a 'delta wing with an enlarged central portion 12. The

center portion 12 is provided with a cavity 14, best shown in FIG. 3, in which may be disposed instruments such as a preamplifier and battery power source, not shown. In the specific embodiment disclosed in FIGS. 1 to 4, the instrumentation is intended for use with a hydrophone 16 extending from the nose of the vehicle. A cover plate 19 extends over the cavity 14. In the particular embodiment shown, it is intended that the preamplifier and battery will be potted to protect the components. In order to minimize drain on the battery, the vehicle is provided with a mercury switch between the battery and amplifier so that the amplifier will not be energized by the battery except when the vehicle is in a generally horizontal position corresponding to its attitude while being towed. While a specific instrumentation carried by the vehicle has been described, it will of course be understood that various other instrumentation for other purposes could be carried.

As will be most clearly apparent from FIGS. 1 and 3, the delta wing of the vehicle consists essentially of two 306090 triangles joined along the longer legs of the triangle. The wing is provided, as shown most clearly in FIG. 4, with negative dihedral. The included angle between the wing section is approximately The delta wing is provided with an air foil section, as shown in FIG. 2. In the specific embodiment shown, the air foil is essentially a Clark-Y air foil with the flat face side of the air foil facing generally upwardly and the camber side facing downwardly. Accordingly, it will be apparent that when the vehicle is flown through the water, a negative lift is developed which tends to depress the vehicle. In accordance with the object of providing a high lift over drag ratio, the air foil section is maintained quite thin. For example, in the specific embodiment of FIGS. 1 to 4, the air foil section has a chord to thickness ratio of approximately 16:1. In any event, the chord to thickness ratio should not be less than approximately 15:1 for high speed operation.

While the negative dihedral of the delta wing provides lateral stability during flight through the water, we have found that at high speeds it is essential to provide an additional vertical stabilizing surface in the form of a vertical stabilizer 18 which extends upwardly from the after section of the body. The stabilizer 18 as disclosed is a triangular shaped flat plate. In order to provide for adjustment of lateral tracking, the stabilizer is mounted on the body by a pivot rod 20 and a bracket 22 spaced longitudinally of the stabilizer from the pivot 20. As shown in FIG. 2, the bracket 22 is provided with a pair of flanges extending laterally from the sides of the stabilizer 18. Each of the flanges has an arcuate elongated slot 24 through which extend clamping screws 26 for locking the stabilizer in adjusted position. The vertical stabilizer tends to balance the lateral area, as viewed in FIG. 3, of the delta wing below the tow point so that in high speed turns better roll stability characteristics are obtained.

In accordance with another aspect of the invention, the dela wing body, as well as the stabilizer 18, are fabricated by fiberglass reenforced resin laminate procedure to provide a very smooth external surface while at the same time providing high impact strength and ruggedness. The body 10 is preferably fabricated in two sections with one section corresponding generally to the top surface of the body and the other section corresponding to the bottom surface. The two sections are laid up separately and then joined by a suitable resin to provide a hollow structure, as shown generally in FIG. 2. The material from which the body is fabricated, as well as the instrumentation carried in the body, have a specific gravity greater than one when the vehicle is out of the water. It has been found that in order to achive stability at high speeds, it is essen tial that the specific gravity of the vehicle be greater than one and a specific gravity of about 1.5 is satisfactory.

i 3 Prior underwater vehicles of this; general type have had neutral, or substantially neutral buoyancy, with the result that very poor stability was provided. Too great a specific gravity, such'as in conventional weighted fish, makes-for too much drag causing the fish to tend to rise at moderate tow speeds and placing an undesirably high stress on'the tow cable. In order to assure the desired. specific gravity 1 when the vehicle is in the Water the body of the vehicle 'is provided with small apertures, not shown, whereby the interior hollow sections of the body willbe free flooding, thus eliminating any buoyancy which might be provided I by these hollow sections. Further, it has been found that in order to achieve stabilization in roll at high speeds, it is necessary to provide ballast in the vehicle. Accordingly, in the specific embodiment shown, ballast 28 is molded into the nose or forward portion of the vehicle. This ballast senses gravitational acceleration and thus the vertical so that it maintains the vehicle in level flight. Without this ballast, the vehicle will tend to react as if it were flying in a gravity free field and will not tend to fly in any particular attitude, any attitude being'equivalent to any other as far as the vehicle is concerned.

The vehicle is towed by a cable 30 having a clevis 32 at one end The clevis is pivotally mountedon a shaft 34 pivotally supported at its ends by a pair of bearings 36 duction in drag permits the use of a'lighter cable. Th

cable is'molded from; a suitable plastic which is flexible I and whichwill stand theab'u'se of oceanographic applica 1 tions. Each of the fairingshas an aperture extending longitudinallly therethrough. The aperture is sufficiently larger than the outside diameter of the cable. that each of the fairings is freelymovable about the axis of the cable;

Ina specific embodiment, the fairings were approximately 6 inches long, 1 /2 inches wide and inch thick with a duced morethan 50%. i

While the cable 30 is normally attached directly to the J connectorfid onthe body, it may be desirable in certain instances to-use an'elastic shock cord at the surface end. 7

of the cable.

For example, when the towing vesselencounters moderate seas and is pitching, the'shockcord mounted on the body 10; The pivotal axis of the clevis extends at-right angles to the longitudinal center line of would isolate the towed vehicle. to eliminateany'transmission ofthepitching motion to the vehicle.

- The vehicle of this invention has much improved stabilizing particularly at high speeds. A testv'ehiclc similar the body while the pivotal axis of the shaft 34 extends 7 parallel to and is in vertical alignment'with the longitudinal axis of the body. Accordingly, there is provided a universal connection between the cable 30 and the body 10. As most clearly shown in FIG. 1, the coverplate 19 I is provided with a'pair of parallel rows of threaded apertures 37. The bearings 36 mounting the shaft 34 are mounted on the cover plate 19 by means of screws extending into the apertures 37. As will be apparent from FIG/l, the tow point of the vehiclemay be adjusted along M the longitudinal axis of the vehicle by adjusting the mounting of the bearings 36 in the apertures 37. Depending upon the instrumentation carried by thevehicle, and particularly the distribution of weight of this instrumentation,

the tow point of the vehicle should 'be adjusted relative to 'to the vehicle of FIGS. 1 to 4.has been successfully towed up (020 knots with excellentstability about theroll, pitch and yaw axes. Withresp'ect to yaw stability, the negative dihedralldelta wing presents'a suflicient lateral area to H generate acorrecting moment when the vehicle deviates.

from a straight course about'the yaw axis. A further particular advantage'and characteristic feature ofa vehicle .of this invention is thelow angle that the tow cable as-I sumes relative to the vertical. For example, in the test vehicle mentioned above towed 'at a depth .on the order 1 of feet andat a tow speed of 15 knots, the. tow angle, as

measuredfrom gthe vertical was only about 102; Thisis the center of pressure CI" of the delta wing in order to achieve the desired flight characteristics 'of the vehicle. In this connection, it has been found that the tow point should be at or forward ofthe center of pressure in vertical and horizontal planesin order to achieve stability and satisfactory performance, particularly at high speeds.

In order to achieve hydrodynamic trim of the vehicle, a pair of wedges or trim members 33 are mounted onthe trailing edge of the Wingonthe camber side thereof. The wedges are fixed or in other words are not adjustable. The trim members are configured specifically vfor each particular installation of instrumentation. The non-adjustability'of the trim members assures that the vehicle will not inadvertently or'otherwise go out of trim during service.

In the use of the vehicle, the cable is of course attached to a towing vehicle. The cable 30 is preferably a coaxial cable serving both 'as a strength 'memberfor towing and also as a means for transmitting signals from contrasted to prior devices where the tow angle, at much lower speeds, would be as muchas 30 The obvious-ark vantageis that the vehicle maybe towedycloser to the towing vessel and with jmaterially less length of cable. A

further advantage and characteristicof the vehicle Of th.l$ V invention and particularly of theembodiment of FIGS; 1 v to 4 isthat the'tow angle will remain constant withthe speed, which is contrary to the casewithconventionally weighted fish and the like.-

" The vehicle is of light weight construction and i s forif example about the weight of conventional fish. As noted above,' the noise level of the faired'cable ispar- V ticularly low.- '.In addition, the smooth surface provided 4 on the -fiberglass body results in very'low noise from the J vehicle itself. Also, where fiberglass reenforced resin is V utilizedv in fabricating thevehicle', it will be acoustically transparent which improves performancafor example, where the vehicle carrieshydrophone installations. Also,

. the vehicle has a materially improved lift over drag ratio;

the instrumentation in thevehicle to the towing vessel. In this connection, the internal, conductors of the cable 30 are connected at one end to the instrumentation of the vehicle and at the other end to the instrumentation of the towing vessel. ,One of the problems-encountered in tow:

ing submerged vehicles for'oceanographic research has been thatof cable noise andfatigue. Accordingly, and as shown in FIG. 5, the cable30 is provided with fairings 40 disposed longitudinally along the cable 30. Each of the fairings as shown in FIG. 6 has a symmetricallystreamlined cross section to minimize drag and cable vibration during towing. The reduction in cable vibration improves fatigue life of the cable components and improves acoustic receiving efliciency. of the overall system. Also,'the refor example,fat 0-20 knots the'ratio is-approximately 521. Therefore, itwould be apparentthatthe' vehicle i in eifect flies through the water utilizing hydrodynamic 'forces rather'thanweight. Asa result, the vehicle will not rise as speed increases within the operating-range of the -.-vehicle.

The connection between the end of a tow 'cable and the vehicle permits the vehicle to fly. freely without'having imposed on it any forces by the cable which will tend; 1 to cause it to mistrack. An additional characteristic fea ture and advantage 'of this inventioniis; that "the .liftto drag'ratio of'the vehicle is substantially.linearbetween,

' from 0+20 knots. Accordingly, a'miniature version of 'the vehicle maybe mounted on the end ofa strainrod or the-likewhereby the strain on the rod isproportional This is contraryto' the performance of a Weightedfish' of the same weight which tends to rise to ,the surface of the water if-the speed exceeds 5 to 6 knots..

aromas to negative lift and thus speed of the vehicle. This strain is measured by a strain gage connected to appropriate instrumentation to provide an accurate speedometer. It will be apparent that the application of the vehicle to speedometcrs could utilize other mounting means such as a resiliently restrained mount, etc. Also, inasmuch as negative lift is proportional to speed, the cable tension is an accurate indication of speed and this effect can be used to provide a speedometer. Another use which has been made of the vehicle is the attachment of one or more of such vehicles to the tow line for an instrumented vehicle to aid materially in straightening the hooked catenary shape of the tow line and thus provide a higher performance system. Further, two similar vehicles have been connected together with the upper one inverted to provide a device for towing such as by helicopter. In this arrangement the upper inverted vehicle acts as a surface vehicle and counteracts the negative lift of the lower vehicle so that the lower vehicle is maintained at a constant depth while being towed, and at the same time, the cable tension is materially reduced. In this combination, the upper inverted vehicle had its tow point at the nose and the lower vehicle was suspended about /3 of the way aft from the nose of the upper vehicle with the point of attachment to the lower vehicle being approximately at the tow point shown in FIG. 1.

A further use contemplated for the vehicle of this invention is in controlling and depressing fishing trawls whereby a plurality of vehicles attached to the net would operate to maintain the mouth of the net open and at the same time depress the trawl. It is intended that in such a use only mid-water trawling would be attempted. Further, it is contemplated that a vehicle utilized both to open the mouth of the net and depress the trawl would be flown at about a 45 angle about the roll axis. This roll attitude is maintained by weighting one side only of the delta wing with ballast and providing buoyancy, such as by a sealed air chamber, along the center line of the vehicle. The ballast provides the necessary unbalance to maintain the vehicle in the desired roll attitude and the buoyancy provides a reference for the vehicle for this purpose.

An alternative embodiment of the invention is shown in FIGS. 7 and 8. In this embodiment, the vehicle is basically identical with the vehicle of FIG. 1, in the corn struction and configuration of the body 10 and tail 18. However, in the embodiment of FIG. 7, the vehicle is provided with an automatically compensating tow point. The clevis connection of the cable 30 is pivotally mounted to a slide 44 slidably and pivotally mounted on a bar extending fore and aft along the center line of the vehicle. The slide 44 is thus movable fore and aft and is also movable about the axis of the bar. A coil spring 46 biases the slide 44 toward the stern of the vehicle. As will be apparent from the above and FIG. 7, as the drag of the vehicle increases the tow point will move forward. This will compensate for a forward movement of the center of pressure as the speed of the vehicle is increased. This improves the stability of the vehicle, particularly where it is operated over a wide range of speeds. The embodiment of FIG. 7 further includes a faired member 43 depending from the center of the underside of the body. The faired member 48 substantially improves high speed stability of the vehicle. As shown in FIG. 8, the faired member 43 has a symmetrically streamlined cross section. While not necessary, in the embodiment of FIGS. 7 and 8, the faired member 48 is hollow and is adapted to carry instrumentation such as an electromagnetic log. As can be seen from FIG. 7, the center of the faired member 48 is located aft of the tow point. The drag created by the faired member will, with respect to the tow point, provide a moment opposite to that provided with respect to the tow point and center of lift. In one aspect of this embodiment the faired member 43 is dimensioned so that this counter balancing moment substantially balances out the moment created with respect to the tow I point and center of lift thus tending to maintain a conant angle of attack throughout the normal range of speed of the vehicle. Without this faired member, it has been found that as the towing speed increases, the angle of attack tends to decrease. While this might not be important in most applications, there are applications wherein it is desirable, if not essential, to assure that the vehicle maintains a constant attitude about the pitch axis or in other words a constant angle of attack.

nasmuch as many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, we claim:

1. An underwater towed vehicle for towing behind a towing vehicle by means of a cable extending generally vertically from the towing vehicle, said towed vehicle having a body in the form of a delta shaped wing having a negative dihedral, said body having an airfoil section with a chord to thickness ratio of at least 15:1, and a tow point on said body, said tow point being positioned forward of the lateral center of pressure of said body when said vehicle is under tow and said tow point being positioned no further aft on said body than the longitudinal center of pressure thereof.

2. An underwater towed vehicle for towing behind a towing vehicle by means of a cable extending generally vertically from the towing vehicle, said towed vehicle having a body in the form of a delta shaped wing, said wing being defined by a pair of 30-60-90 triangles joined at a straight line of intersection along the legs thereof opposite the 60 angles thereof respectively, said body in the form of a delta shaped wing having a negative dihedral and relatively thin airfoil section with a chord to thickness ratio of at least 15:1, the tips of said wing being free of planar surfaces having upward lift characteristics, and a tow point on said body, said tow point eing forward of the lateral center of pressure of said body when said vehicle is under tow and being positioned no further aft on said body than the longitudinal center of pressure thereof.

3. An underwater towed vehicle as defined in claim 1 further including a vertical stabilizer on said body extending from the aft portion thereof and trim members mounted on the trailing edge of said wing.

References Cited in the file of this patent UNITED STATES PATENTS 168,432 Trenchard Oct. 5, 1875 708,553 Holland Sept. 9, 1902 1,400,211 Burney Dec. 13, 1921 2,414,480 Morrill Jan. 21, 1947 2,524,863 White Oct. 10, 1950 2,891,501 Rather June 23, 1959 2,960,960 Fehlner Nov. 22, 1960 2,980,052 Fehlner Apr. 18, 1961 2,987,029 Manuel June 6, 1961 3,005,438 Muldowney Oct. 24 1961 3,005,973 Kietz Oct. 24, 1961 3,024,757 Aschinger Mar. 13, 1962 3,062,171 Somerville Nov. 6, 1962 FOREIGN PATENTS 420,825 Italy Mar. 6, 1947 OTHER REFERENCES Ower, E., and Naylor, I. L.: High Speed Flight, New York Philosophical Library, 1957 p. 67 TL551.509. 

1. AN UNDERWATER TOWED VEHICLE FOR TOWING BEHIND A TOWING VEHICLE BY MEANS OF A CABLE EXTENDING GENERALLY VERTICALLY FROM THE TOWING VEHICLE, SAID TOWED VEHICLE HAVING A BODY IN THE FORM OF A DELTA SHAPED WING HAVING A NEGATIVE DIHEDRAL, SAID BODY HAVING AN AIRFOIL SECTION WITH A CHORD TO THICKNESS RATIO OF AT LEAST 15:1, AND A TOW POINT ON SAID BODY, SAID TOW POINT BEING POSITIONED FORWARD OF THE LATERAL CENTER OF PRESSURE OF SAID BODY WHEN SAID VEHICLE IS UNDER TOW AND SAID TOW POINT BEING POSITIONED NO FURTHER AFT ON SAID BODY THAN THE LONGITUDINAL CENTER OF PRESSURE THEREOF. 